Ballasts for gaseous discharge lamps



May 5, 1959 Filed Oct. 10, 1956 B. K. NASTER BALLASTS FOR GASEOUSDISCHARGE LAMPS 5 Sheets-Sheet 1 INVENTOR.

Ber-i K Naszer May 5, 1959 B; K. NASTER BALLASTS FOR GASEOUS DISCHARGELAMPS 5 Sheets-Sheet 3 Filed Oct. 10, 1956 INVENTOR- BERT K. NASTER 1 gz, 9% WJZAWHM AT TYs,

y 5, 1959 B. K. NASTER 2,885,597

BALLASTS FOR GASEOUS DISCHARGE LAMPS Filed Oct. 10, 1956 5 Sheets-Sheet4 r z I62 6 '26 200 202 340 115 V AC.

NVENTOB BERT K. NASTER ATTYs.

y 1959 B. K. NASTER 2,885,597

BALLASTS FOR GASEOUS DISCHARGE LAMPS Filed Oct. 10, 1956 5 Sheets-Sheets ZOU QM NVE'NTQR.

BERT K. NASTER 1 @m,% QM -M m ATTYS.

United States Patent 2,885,597 BALLASTS FOR GASEOUS DISCHARGE LAMPS BertK. Naster, Hollywood, Fla. Application October 10, 1956, Serial No.615,128 Claims. ((11. 315-138) This invention relates to .new andimproved ballasts for use in starting and operating fluorescent lamps orother gaseous discharge lamps. More specifically, the present inventionrelates to lead-lag ballasts adapted to operate one fluorescent lampwith leading current, while operating another lamp with lagging current.Thus the currents through the lead and lag lamps differ substantially inphase. The phase difference will approach 90. With this type ofarrangement, the phase difference in the lamp curents minimizes thecombined stroboscopic effect of the lamps. Moreover, a lead-lagballasting arrangement of this character will operate at a high powerfactor, approaching unity, rather than at the low power factorscharacteristic of inductive ballast arrangements. This application is acontinuation in part of my co-pending application, Serial No. 543,069,.filed October 27, 1955, and now abandoned.

One object of the present invention is to provide a new and improvedlead-lag ballast which will operate at a substantially higher powerfactor than has heretofore been obtained with commercial lead-lagballasts.

A further object is to provide a new and improved lead-lag ballast whichwill provide ample voltage for starting the lamps.

Another object is to provide a new and improved leadlag ballast whichtends to start the lead and lag lamps sequentially, the starting of thelead lamp being effective to increase the starting voltage applied tothe lag lamp.

It is a further object to provide a .new and improved lead-lag ballastwhich may readily be varied in construction to obtain the maximumpossible power factor, simply by changing the position of a tap on oneof the windings, without any necessity for changing the construction ofthe laminated core for the'ballast.

Another object is to provide a new and improved leadlag ballast wherebythe waveform of the current through the lead lamp is improved, with theresult that the ballast will operate with lower losses and at a higherpower factor, and Will operate the lead .lamp with enhanced brilliance.

A further object is to provide a new and improved lead-lag ballastwhereby the lamp currents and the power delivered to the lamps willremain nearly constant over an extremely wide range of input voltage.

Another object is to provide anew and improved leadlag ballast whichwill achieve improved balance between the lead and lag lamps, withrespect to lamp current, power consumption and brilliance.

It is another object to provide a new and improved lead-lag ballastcapable of operating lamps with enhanced power input and brilliance,yet'with reduced'lamp current with resulting prolongation in lamp life.

A further object is to provide a new and improved lead-lag ballast whichwill operate the .lamps with improved brilliance, yet with low inputcurrent to the ballast and low losses therein, with the result that theballast will operate at a high power factor and with high elficiency,

but at a low operating temperature and with a minimum of noise and hum.

It is a further object to provide a new and improved lead-lag ballastcapable of operating at high efiiciency and with a high power factor andhigh lamp brilliance, while utilizing inexpensive grades of cold rolledsteel in the core, rather than the expensive grades of silicon steelusually employed.

Further objects and advantages of the present invention will appear fromthe following description, taken with the accompanying drawings, inwhich:

Fig. l is a plan view of an exemplary ballast constituting afirstillustrative embodiment of the invention.

Fig. 2 is an elevational sectional view taken generally along a line 2-2in Fig. 1.

Fig. 3 is a schematic wiring diagram of the illustrative ballast of Fig.1.

Fig. 4 is a plan View of another ballast, constituting a secondillustrative embodiment of the invention.

Fig. 5 is an elevational sectional view taken generally along line 5-5in Fig. 4.

Fig. 6 is a schematic wiring diagram of the ballast of Fig.4.

Fig. 7 is a diagrammatic view showing the waveform of the lead lampcurrent for the ballast of Figs. 4-6.

Fig. 8 is a plan view of another ballast constituting a thirdillustrative embodiment of the present invention.

Fig. 9 is an elevational sectional view taken generally along a line 9-9in Fig. 8.

Fig. 10 is a schematic wiring diagram of the ballast of Fig. 8.

Fig. 11 is a diagrammatic view showing the waveform of the lead lampcurrent for the ballast of Figs. 8-10.

Fig. 12 is a schematic wiring diagram of another modifled ballast foroperating only one lamp.

Fig. 13 is a plan view of still another ballast constituting anotherillustrative embodiment of the present invention.

Fig. 14 is an end elevational view of the ballast of Fig. 13.

Fig. 15 is a schematic wiring of Fig. 13.

Fig. 16 is a diagrammatic view showing the waveform of the lead lampcurrent for the ballast of Fig. 13.

If the drawings are considered in greater detail, it will be seen thatFigs. 1-3 illustrate a ballast 10 adapted to start and operate two lamps12 and 14, which may be fluorescent lamps or other gaseous dischargelamps. It will be understood that each of the two lamps may be replacedwith two or more shorter lamps connected in series.

It will be seen from the Fig. 3 that the illustrative former 16 whichpreferably diagram of the ballast schematic wiring diagram of ballast 10comprises a transis arranged and connected as an auto-transformer. Inthis instance, the transformer 16 is provided with a primary winding 18,together with two secondary winding circuits adapted to operate thelamps 12 and 14.

The primary winding 28 may be energized from an ordinary alternatingcurrent power line 2! adapted to supply some suitable voltage, such as118 volts. Itwill be realized that the transformer 16 may be arranged tooperate on any other desired line voltage. The illustrated power line 20includes a pair of line wires 22 and 24. It will be seen that a lead 26extends directly between one end of the primary winding 18 and the linewire 24. A circuit may be traced from the other end of the primary 18 tothe line wire 22 through a lead .28, contacts 30 and 32, a lead v34,c0ntacts36 and 38, and a lead 40. The contacts 30 and 32 are adapted to.engage a terminal electrode 42 at one end of the lamp 14.

--e,sse,eer 1 r Likewise, the contacts 36 and 38 are arranged to engagean electrode 44 at one end of the lamp 12. It will be seen that theterminal electrodes 42 and 44 complete the energizing circuit to theprimary winding 18 by establishing connections between the contacts 30and 32, in the case of the electrode 42, and the.contacts 36 and 38, inthe case of the electrode 44. If either of the lamps 12 or 14 isremoved, the energizing circuit to the primary winding 18 isautomatically broken.

The illustrated secondary circuit to energize the lamp 12' comprises alead circuit secondary winding 46 and a swing secondary winding 48. Acapacitor 50 is also provided in the energizing circuit for the lamp 12,so that thelamp will operate on a leading current. The energizingcircuit for the lamp 12 may be traced between the line wires24 and 22through the lead 26, a lead 52, the entire swing secondarycwinding 48,alead 54, the lead secondary winding 46, a lead 56, the capacitor 50, a

lead 58, a contact 60, a terminal electrode 62 on the lamp 12, thegaseous discharge in the lamp 12, the electrode 44, the contact 38, andthe lead 40. It will be seen that a safety resistor 64 of high value isconnected across the capacitor 50 to discharge the capacitor when thelamps are turned off. This arrangement largely eliminates the shockhazard that would be present if the capacitor were left charged.

It will be recognized that the leads 52, 54 and 56 connect the secondarywindings 46 and 48 in series with the, primary winding 18 and thecapacitor 50 to define the energizing circuit for the lead lamp 12. Inthis instance, all of the windings 18, 48 and 46 are connectedadditively so that the total open circuit voltage of the 'three windingsis the sum of the individual voltages.

The energizing circuit for the lamp 14 comprises a lag circuit secondarywinding 66, together with a portion of the secondary circuit for thelead lamp 12. In this instance, the swing winding 48 is wound in twoportions 68 and 70 with a tap 72 therebetween. The first portion 68 ofthe swing secondary winding 48 is utilized in the circuit for the laglamp 14, as Well as in the circuit for the lead lamp 12. The energizingcircuit for the lag lamp 14 may be traced between the line wires 24 and22 through the lead 26, the lead 52, the first portion 68 of the swingwinding 48, the tap 72, a lead 74, the lag secondary winding 66, a lead76, a contact 78, a terminal electrode 80 on the lamp 14, the gaseousdischarge in the lamp 14, the electrode 42, the contact 32, the lead 34,the contact 36, the electrode 44, the contact 38 and the lead 40. Thus,the leads 52 and 72 connect the windings 18 and 66 and the windingportion 68 in series. In this instance, all three of the windingelements 18, 66 and 68 are polarized so that the windings are additive.

The windings on the transformer 16 may be arranged in various ways, butin this instance, the lag winding 66 is loosely coupled to the primarywinding 18 so that there will be considerable leakage flux between thewindings. Accordingly, the winding 66 has a fairly high leakagereactance so as to limit the operating current through the lamp 14. Dueto the inductive reactance of the winding 66, the lamp 14 draws alagging circuit.

The lead winding 46 is preferably coupled more closely than the lagwinding 66 to the primary Winding 18. In this way, the leakage reactanceof the lead winding 46 will be relatively low. Moreover, the voltageinduced from the primary winding 18 will be close to the maximumpossible value. The coupling between the swing winding 48 and theprimary winding 18 may be varied to a considerable extent, but in thisinstance is somewhat closer than that between the lag winding 66 and theprimary winding 18. At the same time, the swing winding 48 is coupledsomewhat less closely than the lead winding 46 to the primary winding18. Thus, the swing winding 48 has a fairly high leakage reactance, allof which is in the lead circuit and part of which is in the lag circuit.In the energizing circuit for the lead lamp 4 12, the reactance of thecapacitor 50 exceeds that of the windings 46 and 48. Thus, the lamp 12draws a leading current which is limited by the capacitor 50.

The coupling relationships among the windings 18, 46, 48 and 66 on thetransformer 16 might be secured in various ways. However, one suitableand advantageous arrangement for the transformer 16 is shown in Figs. 1and 2. It will be seen that the transformer 16 includes a magneticcore82 composed of a stack of laminations 84. The illustratedcore 82 has anouter, generally rectangular ring-shaped member 84 and a central legmember 86. It will be seen that the central leg 86 extends betweenopposite end legs 88 and 90 on the outer core member 84. Elongated sidelegs 92 and 94 are formed on the outer member 84 between the end legs 88and 90. In this instance, the side legs 92 and 94 are considerablyelongated relative to the end legs 88 and 90. This constructionincreases the leakage flux in the transformer 16. The joints between thecenter member 86 and the outer member 84 also increase the leakage flux.

The illustrated central leg 86 may be considered to have two endportions 96 and 98 and an intermediate portion 100. In this embodiment,the primary winding 18 is mounted on the. intermediate portion 100. Thelead winding 46 is wound directly over the primary winding 18 to obtainclose coupling between these windings. It will be seen that the swingwinding 48 and the lag winding 66 are mounted on the end portions 96 and98, respectively, of the central leg 86. The ,end portion 98 is longerthan theend portion 96 and hence is effectively spaced farther from theprimary winding 18. Thus, the coupling between the lag'winding 66 andthe primary winding 18 is even looser than that between the swingwinding 48 and the primary.

In the illustrated transformer 16, the leakage flux is increased bymagnetic shunt elements acting between .the central leg 86 and the sidelegs 92 and 94 adjacent opposite ends of the primary winding 18. Whilethe shunts might take various forms, they are illustrated as projections102 extending inwardly from the side legs 92 and 94 toward the centralleg 86. Two such projections 102 are provided at each end of the primarywinding 18 and are interposed between the primary and the adjacentsecondary windings. The shunts 102 are effective to increase the leakagereactance of the lag winding 66 and the swing winding 48. It will beseen that gaps 104 are provided between the magnetic shunts 102 and thecentral leg 86.

The entire transformer 16 and the capacitor 50 may be mounted in ahousing 106, which may assume various forms but is illustrated as anelongated sheet metal pan with slotted mounting flanges 108 at itsopposite ends.

It will be understood that the number of turns in the various coils ofthe transformer 16 may be varied over a wide range to suit differentconditions and requirements. Likewise, the arrangement of the coils, theshape of the core, and the number and thickness of the laminations inthe core may be varied. Nevertheless, it may be helpful to give theseparticular details of a specific ballast which has been tested and foundto operate in a highly advantageous manner. These details are givenpurely by way of example and are not intended to limit.

the scope of the invention.

In this specific ballast, the primary winding has 800 turns of No. 23gauge wire. The lead winding 46 has 1700 turns of No. 29 gauge wire. ofNo. 29 gauge wire are employed in the swing coil. The portion 68 betweenthe tap 72 and the end lead 52 has 1000 turns which are connected intothe lag circuit. The lag secondary 66 has 2550 turns of No. 28 gaugewire.

In the specific example, the magnetic core 82 is approximately 10 incheslong and 2 inches wide. Thirtythree of the laminations 84 are employedand each lamination is .025 of an inch thick.

Likewise, 1700 turns In the specific exemplary ballast, the value of thecapacitor 50 is about 1.45 microfarads. The leak resistor 64 may have avalue of 6 megohrns.

The specific ballast, described by way of example, is adapted to beoperated at a nominal primary voltage of 118 volts. Under open circuitconditions, the total voltage across the lead lamp 12 is 565 volts andis entirely adequate to start the lead lamp. This voltage represents thetotal of the voltages across the primary 18, the swing coil 48 and thelead coil 46.

Under open circuit conditions, the total voltage devel oped in the lagcircuit and applied across the lag lamp 14 is about 540 volts. Thus, thestarting voltage across the lag lamp 14 initially is somewhat less thanthat across the lead lamp 12. However, as soon as the lead lamp 12 isstarted, the starting voltage across the lag lamp 14 is automaticallyincreased to about 565 volts so that the lag lamp will be fired. Thisincrease of voltage in the lag circuit is brought about by the leadingcurrent drawn by the lead lamp and passing through the portion 68 of theswing coil 48. It will be recalled that the portion 68 is also in thelag circuit. The current through the lead lamp 12 causes a voltage dropin the swing coil 48 due to the leakage reactance of the coil. Becauseof the leading character of the current, however, the voltage drop is sophased that it actually augments the voltage induced in the swing coil48 by the primary winding 18. A portion of this augmented voltage isdeveloped in the winding portion 68 and thereby is applied to the laglamp 14 so as to increase the starting voltage and insure the firing ofthe lag lamp.

Under operating conditions with both of the lamps 12 and 14 lighted, thelead lamp 12 draws leading current, due to the reactance of thecapacitor 56, while the lag lamp 14 drags lagging current due to theinductive reactance of the lag secondary 66. The out-of-phase componentsof the leading and lagging currents tend to neutralize each other, withthe result that the power factor of the ballast is improved and mayclosely approach unity. The position of the tap 2 on the swing coil 4-8affects the balance between the leading and lagging currents. Thus, theposition of the tap may be preselected to obtain the maximum possiblepower factor. With this construction, a power factor between 95 and 100percent can readily be obtained.

The utilization of a portion of the lead circuit in the lag circuitresults in a considerable saving in material and a reduction in theweight and size of the ballast. Since the lead and lag currents areconsiderably out-ofphase, the resultant current in the common portion 68of the lead and lag circuits is considerably less than the arithmeticsum or" the currents. in other words, the lead and lag lamps draw theirpeak currents at different times, with the result that the current inthe common portion of the lead and lag circuits is minimized. Thisaction permits the use of relatively small wire in the swing coil 48.

The illustrated construction considerably reduces the number of turns ofwire required to develop the necessary starting voltage for the lamps.Accordingly, the overall size of the ballast can be made small. The saving in the total number of turns results largely from the utilization ofthe swing coil to energize both the lead and the lag lamps.

Due to the precise balance between the lead and lag currents, theout-of-phase components are substantially neutralized. This actionreduces the total current in the swing coil and also reduces the leakageflux in the core.

Accordingly, the size of the core and the amount of copper employed inthe windings may be reduced to a minimum. The reduction in total currentand in leakage flux reduces the losses in the ballast, with the resultthat less heat is generated. Thus, the amount of copper and iron in theballast can be reduced without causing the 122 is connected to the lead6 ballast to rise in operating temperature above established limits.

The voltage in the lead and lag circuits is relatively low since thevoltage need only be sufiicient to start a single lamp. The relativelylow voltage is an advantage from a safety standpoint. Moreover, the lowvoltage requirements obviate any need for employing extremely fine wirein the secondary windings. Such wire is exensive and leads to increasedwinding cost. Moreover, the low voltage employed in the ballastvirtually eliminates any danger of breakdown in the insulation.

The illustrated ballast of Figs. 1-3 operates the two lamps 12 and 14 insuch a manner that the combined stroboscopic efiect is minimized. Due tothe provision of the capacitor 50, the lamp 12 draws leading current. Onthe other hand, the lamp 14 draws lagging current because of theinductive reactance of the windings 66 and 68 in the lag circuit. Thus,the currents in the lead and lag lamps 12 and 14 are substantiallydegrees out-of-phase. Accordingly, the current in one lamp 12 is at ornear its maximum point when the current in the other lamp is passingthrough its Zero point. With the currents thus staggered, thestroooscopic effect is largely eliminated.

The connection of the lag circuit to the tap '72 on the swing coil 43has the effect of matching the impedances in the lead and lag circuitsso as to provide maximum power factor and etficiency. If the dischargein one lamp is extinguished due to a fault in the lamp or some othercause, the other lamp remains in operation. In other words, thecontinued operation of each lamp is independent of that of the otherlamp.

Fi s. 4-7 illustrate a second ballast which in many res ects is quitesimilar to the ballast It) of Figs. 1-3 but in other respects representsa significant improvement over the bailast or" Figs. 1-3. Thus, theballast 120 comprises a primary Winding 122 which is connected acrossline wires 124 and 126 by a circuit which may be traced through acontact 128, a lamp terminal 130, a contact 13-2, a lead 134, a contact136, a lamp terminal 138, a contact 1%, and a lead 142. It will be seenthat the line wire 124 is connected to the contact 128, while the linewire 126 is connected to one side of the primary winding 122. The otherside of the primary winding 142. The lamp terminals 130 and 13:1 are onfluorescent lamps 14d and 14-6. The lamp 14 1 is the lead lamp, whilethe lamp 146 is the lag lamp. When the lamps 1 14 and 1 16 are in theirnormal operating positions, the lamp terminals 130 and 1321 close theprimary circuit so that the primary winding 122 will be energized fromthe line wires 124 and 126. If either of the lamps 144 and 146 isremoved, the primary winding 122 will be disconnected from the linewires 124 and 126. It will be understood that the line wires 124 and 126may be connected to a suitable source of alternating current which maybe at 118 volts and 60 cycles, or some other suitable voltage andfrequency.

The ballast 1213 is of the auto-transformer type and thus includes alead circuit winding 150, a lag circuit winding 152, and a swing winding154-. The lead and lag windings 150 and 152 are arranged in lead and lagcircuits to energize the lead and lag lamps 14- and 146, which the swingwinding is common to both circuits. Thus, one primary lead 156 on theswing winding 154 is connected to the line wire 126, and thence to oneside of the primary winding 122. The other primary lead 158 of the swingwinding 154 is connected to one terminal lead 160 of the lead winding150. The other primary lead 162 of the swing Winding 150 is connected toone side of a capacitor 164. it will be seen that a lead 166 isconnected between the other side of the capacitor 164 and a contact 168which engages a terminal or electrode 170 on the lead lamp 144. A leakresistor 171 is connected across the capacitor 164 to insure that thecapacitor will be discharged when the lamps 144 and 146 are turned 011.

In this case, the swing winding 154 is provided with a tap 172 which isconnected to one terminal lead 174 on the lag winding 152. The otherterminal lead 176 of the lag winding 152 is connected to a contact 178which engages a terminal or electrode 180 on the lag lamp 146.

The swing winding 154 and the lead winding 150 are so connected that thevoltages developed by these windings are additively related to thevoltage across the primary winding 122. Likewise, the voltage developedby the lag Winding 152 is additively related to the primary voltages andthe portion of the swing coil voltage developed between the lead 156 andtap 172. This portion 182 of the swing coil 154 is in series with thelag coil 152.

In this case, the transformer windings 122, 150, 152 and 154 arearranged in an improved manner on a core 184 made of iron, steel orother highly permeable material. It will be seen that the core 184 has astraight, elongated central leg 186 which supports the four wind ings122, 150, 152 and 154. The leg 186 may be considered to have twoadjacent central portions, 188 and 190 and two end portions 192 and 194.It will be seen ,that the primary and lead coils 122 and 150 arearranged end to end on the central portions 188 and 190, while the lagand swing coil 152 and 154 are mounted on the end portions 192 and 194.The lead coil 190 is positioned between the primary 188 and the lag coil192, on one end of the primary coil 188, while the swing coil 194 is onthe other end of the primary coil.

In the ballast of Figs. 4-7 all of the secondary windings, 150, 152 and154 have substantial leakage reactances. These reactances are due toseveral factors, including the elongated configuration of the centralleg 186 and the end to end disposition of the coils and the spacingbetween the coils. Thus there is a substantial leakage flux between thelead coil 150 and the primary winding 122, due to the elongatedcharacter of these coils and the arrangement of the coils in end to endrelation. The lag coil 152 is spaced farther from the primary winding122 than the lead coil 190, and hence has a higher leakage reactance.Likewise, the swing coil 154 is spaced from the primary 122 and hencehas a relatively high leakage reactance.

The leakage reactances of the lag coil 152 and the swing coil 154 areincreased by the interposition of magnetic shunts 200 and 202 betweenthe primary coil 122 and the coils 152 and 154. More specifically, theshunt 200 is interposed between the lag coil 152 and the lead coil 150,while shunt 202 is interposed between the swing coil 154 and the primarywinding 122. While the shunts 200 and 202 might be formed in variousways, they are shown as projections on an elongated, rectangular,generally box shaped core member 204 which extends around the centralmember 186. The rectangular member 204 has side legs 206 and 208 whichare substantially parallel to the central member 186, together withrelatively short end legs 210 and 212 which extend at right angles tothe central leg 186. In this case, the end legs 210 and 212 have notches214 and 216 therein which receive the ends of the central leg 186. Apartial gap 220 of air or other non-permeable material may be providedbetween one end of the central leg 186 and the end members 210, todefine saturable portions 220 on the end of the central leg 186. It willbe seen that the shunt 200 is in the form of a pair of projections 222extending inwardly from the members 206 and 208 toward the central leg186. Likewise, the shunt 202 takes the form of a pair of projections 224on the legs 206 and 208, extending inwardly toward the central leg 186.Gaps 226 and 228 of air or other non-magnetic material may be providedbetween the projections 222 and the central leg 186. In like manner,gaps 228 may be provided between the central leg 186 and the projections224.

While the number of turns in the windings 122, 150,

152 and 154 may be varied, it may be of interest to give the coil datafor an actual example of a successful ballast of the type shown in Figs.4-6. In the example, the primary winding had 700 turns of #22 gaugeWire, while the lead coil 150 had 1560 turns of #29 gauge wire. The lagcoil had 2450 turns of #29 gauge wire, while the swing winding 154 had1660 turns of #29 gauge wire. The portion 182 between the end lead 156and the tap 172 had 940 turns. This exemplary ballast developed a leadlamp starting voltage of about 550 volts with a primary voltage of about118 volts. This voltage was sufiicient to effect instant starting of thelead lamp 144. Initially, the lag lamp starting voltage was somewhatless than the lead lamp voltage, but as soon as the lead lamp wasstarted, the lag lamp voltage increased to 570 volts, sufiicient toeffect the instant starting of the lag lamp. The increase in thestarting voltage for the lag lamp is due to the leading current drawn bythe lead lamp 144 through the swing winding 154. Due to the leakagereactance of the swing winding 154 the leading current causes thevoltage at the tap 172 to increase. This voltage is applied to the laglamp 146, and is so phased that it enhances the starting voltage for thelag lamp 146.

With the ballast 120 of Figs. 4-6 there is a significant amount ofinductive reactance in series with both the lead lamp 144 and the laglamp 146. In the circuit for the lead lamp 144, the lead winding has aconsiderable inductive reactance due to its arrangement in end to endrelation to the primary winding 122, along the elongated central leg 186of the core. In addition the swing coil 154 has a fairly high inductivereactance, due to the spacing between the swing coil 154 and the primary122, and the provision of shunt 202 between the coils. V In the circuitfor the lag lamp 146, the lag winding 152 has a high inductivereactance, due to the very considerable space between the lag winding152 and the primary winding 122, the provision of the shunt 200 betweenthe windings. Moreover, a portion of the inductive reactance on theswing coil 154 is in series with the lag coil 152 due to the connectionof the lag coil to the tap 172.

It will be understood that there is also a high capacitive reactance inthe circuit for the lead lamp 144 due to the provision of the capacitor164. It is the capacitor 164 which causes the lamp 144 to draw a leadingcurrent.

The waveform of the current in the lead lamp 144 is greatly improved dueto the high inductive reactances in the circuit for the lamp. Fig. 7shows an oscillogram 232 representing the improved waveform of the leadlamp current for the ballast of Figs. 4-6. It will be seen that thewaveform is quite flat topped and smooth and is free from any clips orsharp peaks. The waveform indicates that only a relatively small amountof harmonic content is present in the lead lamp current. By way ofcomparison, Fig. 7 also shows an oscillogram 234 representing the leadlamp current in a prior ballast, not having high inductive reactance inthe circuit for the lead lamp. It will be seen that the oscillogram 234has a sharp dip 235 between two relatively sharp peaks 238 and 240.These irregularities in the waveform indicate that a relatively largeamount of harmonic content is present in the lead lamp current.

The improved waveform of the lead lamp current increases the powerconsumption in the lead lamp and the brilliance of the lamp, whilereducing the lamp current. Accordingly, the life of the lamp isprolonged. The improved lead lamp waveform also improves the waveform ofthe lag lamp current, with resulting increase in lag lamp powerconsumption and brilliance.

As a result of the improved lamp current waveform and reduced lampcurrent, the ballast operates with reduced losses and hence at a lowertemperature. Moreover, the ballast generates a minimum of noise andburn.

The improvement in the waveform raises the power factor of the ballastsubstantially and also effects a substantial increase in the efiiciencyof the ballast. With silicon steel or other high grade magnetic materialin the core 184, a power factor of 96 to 98% may be obtained. This ishigher than is commercially required, with the result that inexpensivecold rolled steel may be substituted for the expensive silicon steel,while still achieving a power factor of 90%, which is fully acceptablecommercially. Thus, the improved ballast makes possible a choice betweena design that will give practically unity power factor and a much lessexpensive design that will still give a commercially acceptable powerfactor.

Due to the reduced lead lamp current, the voltage across the capacitor164 is substantially reduced, with the result that a less expensivecapacitor may be employed without danger of voltage breakdown.

With the high inductive reactance in the lead and lag circuits, theballast of Figs. 46 gives an improved balance between the lead and laglamps 144 and 146 with regard to lamp current, power consumption andbrilliance. Moreover, the self-regulating action of the ballast isgreatly improved. Thus, the lamp currents remain nearly constant over awide range of primary voltage. It has been observed that there is onlyan insignificant change in the lamp currents and the primary currentwhen the primary voltage is varied between 105 and 125 volts. The lampswill start with only 85 volts impressed across the primary.

In the ballast of Figs. 4-7 the swing coil 154 supplies starting voltageand inductive reactance for both the lead and the lag circuits. Thisarrangement brings about a substantial saving in material and space. Inother words, this arrangement makes the ballast more economical and morecompact.

Figs. 8-11 illustrate another ballast 250 which is also highlyadvantageous but is somewhat different in construction than the ballast120. However, the circuit for connecting the ballast 250 between thepower line wires 124 and 126 and the lamps 144 and 146 is much the sameas in the case of the ballast 120. Accordingly, the same referencecharacters have been employed in Fig. as in Fig. 6 for the variouscircuit components which remain the same.

It will be seen that the ballast 250 of Figs. 8-11 comprises a primarywinding 252, a lead winding or coil 254, a lag coil 256, and a swingcoil 258. As in the arrangement of Fig. 6, one terminal lead 260 of theprimary winding 252 is connected to the line wire 126, while the otherterminal lead 262 is connected to the lead 142. Thus, the voltage acrossthe line wires 124 and 126 is impressed across the primary winding 252.

The swing coil 258 and the lead coil 254 are connected in series withthe primary voltage to energize the lead lamp 144. Thus, one terminallead 264 of the swing coil 258 is connected to the terminal lead 260 ofthe primary winding 252. The other terminal lead 266 of the swing coil258 is connected to one terminal lead 268 on the .lead coil 254. Theother terminal lead 270 of the lead coil 254 extends to the capacitor164 and thence to the lead lamp 144.

.In the exemplary ballast 250 the entire swing coil 258 is also in thelag circuit, along with the lag coil 256. Thus, one terminal lead 272 ofthe lag coil 256 is connected to the terminal lead 266 of the swing coil258. The other terminal lead 274 of the lag coil 256 extends tothecontact 178 and thence to the lag lamp 146.

In the ballast 250 of Figs. 8-11, the windings 252, 254, 256 and 258 areprovided with a core 280 made of iron, steel or other highly permeablematerial. It will be seen from Fig. 8 that the core 280 has a centralleg 282 on which the coils 252-258 are mounted. The central leg 282 maybe considered to have two end portions 284 and 286 and two intermediateportions 288 and 290. In this case the lag coil 256 and the swing coil258 are on the end portions 284 and 286, while the lead .coil

10 254 and the primary coil 252 are on the intermediate portions 288 and290, much as in the ballast 148 of Figs. 47. However, in the case of theballast 250, the swing coil 258 is in end to end relation to the primarycoil 252. The lead coil 254 and the lag coil 256 are spaced from theopposite end of the primary coil 252. It will be seen that the lead coil254 is between the coil 252 and the lag coil 256 as in the ballast 128of Figs. 4-7.

Due to the arrangement of the coils, the lead, lag and swing coils 254,256 and 258 have significant inductive reactances. The lag coil 256being most distant from the primary coil 252, has a high inductivereactance, while the lead and swing coils 254 and 258 have smallerinductive reactances.

The inductive reactances of the lead and lag coils 254 and 256 areenhanced by shunts 294 and 296. It will be seen that the shunt 294 isbetween the primary coil 252 and the lead coil 254, while the shunt 296is between the lead coil 254 and the lag coil 256. Thus both of theshunts 294 and 296 are between the primary and the lag coils 252 and256.

From Fig. 8 it will be seen that the shunts 294 and 296 take the form oftwo pairs of inward projections 298 and 380 on a rectangular boxlikecore member 302 extending around the central leg 282 of the core 280.The projections 298 and 300 extend inwardly toward the central leg 282from longitudinal legs 304 and 306 of the rectangular core member 302.As already indicated, the projections 298 are between the primary andlead coils 252 and 254, while the projections 380 are between the leadand lag coils 254 and 256. The projections 300 are somewhat wider thanthe projections 298 and thus have a greater shunting action. Gaps 308and 310 are provided between the central leg 282 and the projections 298and 300.

The central leg 282 extends between relatively short end legs 312 and314 of the rectangular core member 302. Notches 316 and 318 are formedin the end legs 312 and 314 to receive the ends of the central leg 282.Partial gaps 320 and 322 of non-magnetic material are defined betweenthe ends of the central leg 282 and the end legs 312 and 314. However,reduced portions 324 and 326 of the ends of the central leg 282 directlyengage the end legs 312 and 314 to define saturable elements in themagnetic circuit, whereby the leakage flux will be greater underoperating conditions than under starting conditions.

As already indicated, all of the secondary windings 254, 256 and 258have significant inductive reactances. Thus there is considerableinductive reactance in the circuits for both the lead and lag lamps 144and 146. The inductive reactances of the lead and swing coils 254 and258 are in series with the lead lamp 144, along with the capacitivereactances of the capacitor 164. The inductive reactances of the lag andswing coils 256 and 258 are in series with the lag lamp 146. Thereactances in series with the lead and lag lamps 144 and 146 define andlimit the normal operating currents of the lamps.

While the number of turns in the windings 252258 may be varied, it willbe of interest to give the coil data for an exemplary ballast. In anexemplary ballast the primary coil 252 had 450 turns of No. 23 gaugewire, the lead coil 254 had 1200 turns of No. 29 gauge wire, the lagcoil 256 had i300 turns of No. 29 gauge wire and the swing coil had 580turns of No. 29 gauge wire.

It "will be noted that in both of the ballasts and 250, the lead coil isbetween the primary coil and the lag coil. This arrangement results inimproved balance between the lead and lag lamps 144 and 146 with regardto current, power consumption and brilliance. Moreover, this arrangementimproves the waveform of the lamp currents, particularly the lead lampcurrent. The inductive reactance in the lead lamp circuit also improvesthe lead lamp waveform. Fig. 11 illustrates an oscillogram 330 whichrepresents the waveform of the lead lamp current seems? for the ballast250 of Figs. 8-10. It will be seen that the waveform is relativelysmooth, fiat topped and free from irregularities. These characteristicsindicate that the harmonic content of the current is low. By way ofcomparison, Fig. 11 also illustrates an oscillogram 332 representing thelead lamp current for a prior ballast in which the lead and lag coilswere on opposite ends of the primary. It will be seen that theoscillogram 332 has a dip 334 between two peaks 336 and 338. Theseirregularities indicate the presence of undesirably great harmoniccontent in the lead lamp waveform.

The improved lamp current waveform results in high power factor andefiiciency, along with high lamp brilliance. The lamp current isactually reduced, with the result that lamp life is prolonged. Moreover,the ballast runs cooler and with a minimum of noise and hum.

As in the case of the ballast 120, the ballast 250 offers a choicebetween extremely high power factor, from 96 to 98%, obtainable by usingsilicon steel in the core, and a somewhat lower but commerciallyacceptable power factor of about 90% with the use of ordinaryinexpensive cold rolled steel in the core. The use of an inexpensivegrade of steel brings about a great saving in the cost of the ballasts.

Like the ballast 120, the ballast 250 provides nearly constant lamp andprimary currents over a wide range of primary voltages.

In all of the ballasts thus far described, the swing winding or coil isinductively reactive and hence provides a high impedance source ofvoltage for both the lead and the lag circuits. The high impedance ofthe swing winding results in a greatly improved balance in the lampcurrents of the lead and lag lamps.

In addition, the high impedance provided by the swing winding results inexcellent current wave form in both the lead and lag circuits. In thisway, maximum lamp wattage and brilliance are obtained at normaloperating current.

In the ballasts of Figs. 1-7, the lag circuit is connected to the tap onthe swing coil, and the tap is precisely adjusted so as to match theimpedances and lamp currents in the lead and lag circuits. The preciselyadjusted tap provides maximum efiiciency with maximum lamp currents andlamp brilliance. As a result of the high impedance swing coil, theprecisely adjusted tap connected to the lag circuit, and the improvedarrangement of the coils on the core, each of these ballasts providesexcellent regulation, in that the lamp currents and the primary inputcurrent remain nearly constant over an extremely wide range of inputvoltage to the primary winding. The provision of the precisely adjustedswing coil tap also achieves the maximum level of power factorcorrection. Accordingly, the operating losses are reduced to a minimumand the efficiency is increased to a maximum. Furthermore, quieteroperation of the ballast is obtained. The high impedance lead and lagcircuits reduce the losses in both the core and the windings.

In the ballast of Figs. 8-11, no tap is necessary on the swing coil,because the entire swing coil is in the lag circuit. The swing coil isso arranged and so related to the core and the other coils that theentire coil gives the ideal impedance in the lag circuit.

In the ballasts of Figs. 4-11, the swing coil is located at the oppositeend of the primary coil from the lead coil. Thus, the lead circuit issplit into two coils on opposite ends of the primary coil. Thisarrangement provides a more compact arrangement of the magnetic flux inthe core. In other words, the extent of the magnetic field is reduced.As a result, the mechanical hum and noise produced by the ballast aregreatly reduced so that the ballast operates with greatly improvedquietness. Furthermore, the core losses are considerably reduced and theefiiciency is improved.

Fig. 12 illustrates another modified ballast 340 which is an example ofthe manner in which the ballasts thus far described may be modified soas to operate a single lamp. It will be seen that the ballast 340 ofFig. 12 is the same as the ballast of Figs. 4-7, except that the ballast346 is arranged to operate only one lamp. In this case, the lag lamp 146remains and is operated by the ballast 340, while the lead lamp is notemployed. The line wire 124 is connected directly to the contact 136which is engageable with the terminal 138 on the lamp 146. The leadcircuit of the ballast 3413 is employed to effect power factorcorrection. Thus, the lead or wire 166 is connected directly to theprimary wire 142 rather than being connected to the lead lamp. In thelead circuit for the ballast 340, the primary coil 122, the swing coil154, and the lead coil are connected in series as before. The capacitor164 is connected across the three coils so as to draw leading currentand afiord power factor correction.

The ballast 340 operates in much the same manner as the ballast 120,except that the input current is reduced considerably inasmuch as onlyone lamp is drawing power from the ballast. As before, the ballast 340operates with high inductive impedance in both the lead and lagcircuits. Furthermore, the ballast 340 provides high efliciency, highpower factor, maximum lamp brilliance, quiet operation, and greatlyimproved regulation of lamp brilliance with variations in the inputvoltage. In other words, the single lamp ballast 340 has all of theadvantages of the ballasts previously described.

It will be understood that any of the previously described ballasts maybe converted into a single lamp ballast simply by connecting thecapacitor to the primary return lead rather than to the lead lamp. Inother words, the lead circuit is closed so that the capacitor isdirectly across the series-connected coils in the lead circuit.

Still another illustrative ballast 350 is shown in Figs. 13-16. Theballast 350 is somewhat similar to the ballast 250 in that both ballastsmay employ the same or substantially the same core 280. Accordingly thesame reference characters have been applied to the core 280 in Figs.13-15 as in Figs. 23-10.

However, the arrangement and connection of the ballast windings aresomewhat different in Figs. 13-15 than they are in Figs. 8-10. Morespecifically, the ballast 350 is adapted to operate fluorescent lamps352 and 354 of the type having filamentary electrodes which may beheated electrically to start the lamps. Thus, the lamp 352 has filaments356 and 358 while the lamp 354 has filaments 360 and 362.

It will be seen that the illustrative ballast 350 has a primary winding364 having terminal leads 366 and 368 Which are connected directly tothe power line wires 124 and 126. In this case, there is no swing coilbut there are lead and lag coils 370 and 372. One terminal lead 374 ofthe lead coil 370 is connected to the terminal lead 368, while the otherterminal lead 376 on the lead coil 370 is connected to one side of acapacitor 378. The other side of the capacitor is connected to oneterminal 381) of the filament 358 of the lead lamp 352. A leak resistor332 is connected across the capacitor 378.

To complete the circuit for the lead lamp 352, one terminal 384, of theother lead lamp filament 356 is connected to the power line 124. Theother terminal 386 of the filament 356 is adapted to be connected to theother terminal 388 of the filament 358 by a starting circuit thatincludes an automatic starter switch 390, which may be of any suitableconstruction, so as to close the starting circuit momentarily, when thelead lamp 352 is first energized. When the starting circuit is closed,current flows through the filaments 356 and 358, with the result thatthey are heated sufiiciently to emit electrons. After a brief interval,the starter 390 opens the starting circuit, with the result that an arcdischarge is established in the lead lamp 352.

The starting circuit for the lead lamp 352 may also include acompensating winding 392 which may be connected in series with thestarter 390 between the filament terminals 386 and 388. The compensatingwinding 392 is coupled to the primary winding 370 and is adapted toprovide additional voltage to heat the lead lamp filaments 356 and 358so as to increase the speed with which the lead lamp 352 is started.

In the circuit for the lag lamp 354, one terminal 394 of the lag winding372 is connected to the terminal 368 of the primary winding 364, whilethe other terminal 396 of the lag winding 372 is connected to oneterminal 398 of the lag lamp filament 362. One terminal 400 of the otherlag lamp filament 360 is connected to the line wire 124. To start thelag lamp 354, a conventional or suitable automatic starter 402 isconnected between the other terminals 404 and 406 of the filaments 360and 362. The starter 402 is adapted to close momentarily to heat thefilaments 360 and 362 and then open to establish an arc discharge in thelamp 354.

As already indicated, the core 280 of the ballast 350 may be the same asfor the ballast 250 of Figs. 810. In the case of the ballast 350,however, the primary coil 370 occupies the entire space occupied by theprimary and swing coils 252 and 258 in the ballast 250. In other words,the primary coil 370 occupies the portions 286 and 290 of the centralleg 282.

As in all of the previously described ballasts, the primary coil 364 isadjacent one end of the core 280 and is at the opposite end of the corefrom the lag coil 372. The lead coil 370 is between the primary and lagcoils 364 and 372. Due to the arrangement of the coils and the provisionof the shunts 294 and 296, the lead and lag coils 370 and 372 haveconsiderable leakage reactances.

The compensating winding 392 may be arranged in various ways with regardto the core 280. As shown the compensating winding 392 is wound over thelead coil 370.

The number of turns in the various coils may be varied but it may be ofinterest to give the coil data for an exemplary coil. In this coil, theprimary winding 364 had 650 turns of No. 26 gauge wire, the lead coil370 had 900 turns of No. 28 gauge wire, the lag coil had 770 turns ofNo. 28 gauge wire, and the compensating winding 392 had 145 turns of No.28 gauge wire.

As in the case of all of the previously described ballasts, the ballast350 provides considerable leakage or inductive reactance in both thelead and lag circuits. Thus, the reactive lead and lag windings 370 and372 provide the inductive reactances in the circuits for the lead andlag lamps 352 and 354. Due to the inductive reactances in the leadcircuit and the interposition of the lead coil between the primary coiland the lag coil, the lead coil waveform is greatly improved. Thus, Fig.16 illustrates an oscillogram 410 representing the lead lamp current forthe ballast 350. It will be noted that the waveform of the lead lampcurrent is samooth, fiat topped and free from irregularities. By way ofcomparison, Fig. 16 also illustrates an oscillogram 412 representing thelead lamp waveform for a prior ballast in which the lead and lag coilswere on opposite sides of the primary coil. It will be noted that theoscillograrn 412 has two dips sis and 416 interspersed between threepeaks 418, 426 and 422. The irregularities in the waveform 412 causeloss of lamp brilliance and increased losses in the ballast. Thus, theimproved waveform 410 for the ballast 35%) results in greater lampbrilliance with less lamp current and lower losses. The ballast 350operates at high efiiciency and with a high power factor. The operatingtemperature and the noise produced by the ballast are low. Moreover, asin the case of the other ballasts, ballast 317i) maintains nearlyconstant lamp and primary currents with wide variations of the primaryvoltage.

As already indicated, the high impedance lead and lag circuits in eachof the ballasts reduces the lamp currents and improves the wave formthereof, while actually increasing the lamp brilliance. At the sametime, the volt age across the capacitor in the lead circuit is reducedconside-rably, with the result that there is less chance that thecapacitor will fail due to voltage breakdown. The reduction in capacitorvoltage also makes it possible to re duce the cost of the capacitor.

Various other modifications, alternative constructions and equivalentsmay be employed without departing from the true spirit and scope of theinvention as exemplified in the foregoing description and defined in thefollowing claims.

I claim:

1. In a ballast for gaseous discharge lamps, the combination comprisinga magnetic core, a primary winding thereon, a separate highly reactivelag secondary Winding spaced on said core from said primary winding, aseparate secondary winding on said core, a separate reactive swingsecondary winding on said core and including first and second portionswith a tap therebetween, a lead circuit including a capacitor and leadsconnecting said primary winding, said swing winding and said leadwinding in an additive series with said capacitor, and a lag circuitincluding leads connecting said primary winding, said first portion ofsaid swing winding, said tap and said lag secondary winding in anadditive series, said primary winding being connected in the samedirection in both said lead and lag circuits.

2. In a discharge-lamp ballast, the combination comprising a magneticcore, a primary winding mounted thereon, a separate reactive leadsecondary winding mounted on said core on one end of said primarywinding, a separate highly reactive lag secondary winding spaced on saidcore from said primary winding and beyond said lead secondary winding,said lead secondary winding thereby being disposed on said core betweensaid primary, and said lag secondary windings, a separate reactive swingsecondary winding mounted on said core on the opposite end of saidprimary winding, said primary winding thereby being disposed on saidcore between said lead and swing secondary windings, a capacitor, a leadcircuit connecting said capacitor in series with said primary, lead andswing windings with said primary, lead and swing windings additivelyrelated, and a lag circuit connecting said primary winding and said lagsecondary winding in an additive series with at least a portion of saidswing secondary winding, said primary winding being connected in thesame direction in both said lead and lag circuits.

3. In a ballast for gaseous discharge lamps, the combination comprisinga magnetic core, a primary winding mounted thereon, a separate reactivelead secondary wind ing mounted on said core on one end of said primarywinding, a separate highly reactive lag secondary winding spaced on saidcore from said primary winding and beyond said lead secondary winding,said lead secondary winding thereby being disposed on said core betweensaid primary and said lag secondary windings, a separate reactive swingsecondary Winding mounted on said core on the opposite end of saidprimary winding, said primary winding thereby being disposed on saidcore between said lead and swing secondary windings, a magnetic shuntdisposed between said lead and lag secondary windings, a capacitor, alead circuit connecting said c'apacitor in series with said primary,lead and swing windings with said primary, lead and swing windings additivelyrelated, and a lag circuit connecting said primary winding andsaid lag secondary winding in an additive series with at least a portionof said swing secondary winding, said primary winding being connected inthe same direction in both said lead and lag circuits.

4. In a ballast for gaseous discharge lamps, the combination comprisinga magnetic core, a primary winding mounted thereon, a separate reactivelead secondary winding mounted on said core on one end of said primarysecondary winding,

15 winding, a'separate highly reactive lag secondary winding spaced onsaid core from said primary winding and beyond said lead secondarywinding, said lead secondary winding thereby being disposed on said corebetween said primary and said lag secondary windings, a separatereactive swing secondary winding mounted on said core on the oppositeend of said primary winding, said primary winding thereby being disposedon said core between said lead and swing secondary windings, a firstmagnetic shunt between said lead and lag secondary windings, a secondmagnetic shunt between said primary and swing secondary windings, acapacitor, a lead circuit conmeeting said capacitor in series with saidprimary, lead and swing windings with said primary, lead and swingwindings additively related, and a lag circuit connecting said primarywinding and said lag secondary winding in an additive series with atleast a portion of said swing said primary winding being connected inthe same direction in both said lead and lag circuits.

5. In a ballast for gaseous discharge lamps, the combination comprisinga magnetic core, a primary winding mounted thereon, a separate reactivelead secondary winding mounted on said core on one end of said primarywinding, a separate highly reactive lag secondary winding spaced on saidcore from said primary winding and beyond said lead secondary winding,said lead secondary winding thereby being disposed on said core betweensaid primary and said lag secondary windings, a separate reactive swingsecondary winding mounted on said core on the opposite end of saidprimary winding, said primary winding thereby being disposed on saidcore between said lead and swing secondary windings, a first magneticshunt between said lead and lag secondary windings, a second magneticshunt between said primary and lead secondary windings, a capacitor, alead circuit connecting said capacitor in series with said primary, leadand swing windings with said primary, lead and swing windings additivelyrelated, and a lag circuit connecting said primary winding and said lagsecondary winding in an additive series with at least a portion of saidswing secondary winding, said primary winding being connected in thesame direction in both said lead and lag circuits.

6. In a ballast for gaseous discharge lamps, the combination comprisinga magnetic core, a primary winding thereon, separate first and secondsecondary windings on said core, a separate third secondary winding onsaid core and including first and second portions with a taptherebetween, at least said second and third secondary windings beinghighly reactive, a first circuit including a capacitor and leadsconnecting said primary winding, said third winding and said firstwinding in an additive series with said capacitor, and a second circuitincluding leads connecting said primary winding, said first portion ofsaid third winding, said tap and said secondary Winding in an additiveseries, said primary winding being connected in the same direction inboth said first and second circuits.

7. In a ballast for gaseous discharge lamps, the combination comprisinga magnetic core having an elongated generally rectangular ring portionwith a pair of opposite side legs and a pair of opposite end legs, saidcore having a central longitudinal leg extending between said end legs,said central leg having first and second end portions and anintermediate portion therebetween, said second portion being longer thansaid first portion, magnetic shunt elements projecting from said sidelegs toward said central leg adjacent opposite ends of said intermediateportion, a primary winding on said intermediate portion, a separate leadsecondary winding wound over said primary winding on said intermediateportion, a separate highly reactive lag secondary winding on said secondend portion, a separate reactive swing secondary winding on said firstend portion and having first and second winding portions with a taptherebetween, a capacitor, a lead circuit having leads connecting saidprimary winding, said swing winding, and said lead winding in a firstadditive I6 series with said capacitor, and a lag circuit includingleads connecting said primary winding, said first winding portion ofsaid swing winding,'and said lag Winding in a second additive series,said lead circuit having a higher open circuit voltage than said lagcircuit, said swing winding being effective to induce an increasedvoltage in said lag circuit in response to current in said lead circuit.

8. In a ballast for gaseous discharge lamps, the combination comprisinga magnetic core having an elongated generally rectangular ring portionwith a pair of opposite side legs and a pair of opposite end legs, saidcore having a central longitudinal leg extending between said end legs,said central leg having first and second end portions and anintermediate portion therebetween, a primary winding on saidintermediate portion, a first separate seconding winding wound over saidprimary winding on said intermediate portion, a second separatesecondary winding on said second end portion, a third separate secondarywinding on said first end portion and having first and second windingportions with a tap therebetween, a capacitor, a first circuit havingleads connecting said primary winding, said third winding, and saidfirst winding in a first additive series with said capacitor, and asecond circuit including leads connecting said primary winding, saidfirst winding portion of said third winding and said second winding in asecond additive series, said first circuit having a higher open circuitvoltage than said second circuit, said third winding being effective toinduce an increased voltage in said second circuit in response tocurrent in said first circuits.

9. In a ballast for gaseous discharge lamps, the combination comprisinga magnetic core having an elongated generally rectangular ring portionwith a pair of opposite side legs and a pair of opposite end legs, saidcore having a central leg extending between said end legs, a primarywinding on said central leg, a separate reactive swing secondary windingon one end of said central leg and at one end of said primary winding, alag sec ondary winding on the opposite end of said central leg andspaced thereon from the opposite end of said primary winding, a separatelead secondary winding disposed on said central leg adjacent saidprimary winding, a capacitor, a lead circuit connecting said capacitorin series with said primary, swing secondary and lead secondarywindings, and a lag circuit connecting said primary and lag windings inseries with at least part of said swing secondary winding, said primarywinding being connected in the same direction in both said lead and lagcircuits.

10. In a ballast for gaseous discharge lamps, the combination comprisinga magnetic core having an elongated generally rectangular ring portionwith a pair of opposite side legs and a pair of opposite end legs, saidcore having a central leg extending between said end legs, a primarywinding on said central leg, a separate reactive swing secondary windingon one end of said central leg and at one end of said primary winding, alag secondary winding on the opposite end of said central leg and spacedthereon from the opposite end of said primary winding, a separate leadsecondary winding disposed on said central leg between said primary andsaid lag secondary windings, magnetic shunt means disposed between saidlead and lag secondary windings and extending between said central legand said ring portion, a capacitor, 2 lead circuit connecting saidcapacitor in series with said primary, swing secondary and leadsecondary windings, and a lag circuit connecting said primary and lagwindings in series with at least part of said swing secondary winding,said primary winding being connected in the same direction in both saidlead and lag circuits.

11. In a ballast for gaseous discharge lamps, the combination comprisinga magnetic core having an elongated generally rectangular ring portionwith a pair of opposite side legs and a pair of opposite end legs, saidcore having a central leg extending between said end l7 legs, a primarywinding on said central leg, a separate reactive swing secondary windingon one end of said central leg and at one end of said primary winding, alag secondary winding on the opposite end of said central leg and spacedthereon from the oposite end of said primary winding, a lead secondarywinding disposed on said central leg between said primary and said lagsecondary windings, first magnetic shunt means disposed between saidlead and lag secondary windings and extending between said central legand said ring portion, second magnetic shunt means disposed between saidprimary and swing secondary windings and extending between said centralleg and said ring portion, a capacitor, a lead circuit connecting saidcapacitor in series with said primary, swing secondary and leadsecondary windings, and a lag circuit connecting said primary and lagwindings in series with at least part of said swing secondary winding,said primary winding being connected in the same direction in both saidlead and lag circuits.

12. In a ballast for gaseous discharge lamps, the combination comprisinga magnetic core having an elongated generally rectangular ring portionwith a pair of opposite side legs and a pair of opposite end legs, saidcore having a central leg extending between said end legs, a primarywinding on said central leg, a separate reactive swing secondary windingon one end of said central leg and at one end of said primary winding, aseparate lag secondary winding on the opposite end of said central legand spaced thereon from the opposite end of said primary winding, aseparate lead secondary winding disposed on said central leg betweensaid primary and said lag secondary windings, first magnetic shunt meansdisposed between said lead and lag secondary windings and extendingbetween said central leg and said ring portion, second magnetic shuntmeans disposed between said primary and lead secondary windings andextending between said central leg and said ring portion, a capacitor, alead circuit connecting said capacitor in series with said primary,swing secondary and lead secondary windings, and a lag circuitconnecting said primary and lag windings in series with at least part ofsaid swing secondary winding, said primary winding being connected inthe same direction in both said lead and lag circuits.

13. In a ballast for gaseous discharge lamps, the combination comprisinga magnetic core, a primary winding mounted thereon, a separate reactivelead secondary winding mounted on said core adjacent one end of saidprimary winding, a separate reactive swing secondary winding mounted onsaid core on the opposite end of said primary winding, a capacitor, alead circuit connecting said capacitor in series with said primary, leadand swing windings with said windings additively related, said leadcircuit thereby being divided between said lead and swing windings onopposite ends of said primary winding, a separate highly reactive lagsecondary winding mounted on said core on the opposite end of said leadwinding from said primary winding, said lead winding thereby beingdisposed between said primary winding and said lag winding, and a lagcircuit connecting said primary winding and said lag secondary windingin an additive series with at least a portion of said swing secondarywinding.

14. In a ballast for operating a gaseous discharge lamp, the combinationcomprising a magnetic core, a primary winding mounted thereon, a highlyreactive lag secondary winding spaced on said core from one end of saidprimary winding, a separate reactive swing secondary winding mounted onsaid core on the opposite end of said primary winding, a lag circuitconnecting said primary winding and said lag secondary winding in anadditive series with at least a portion of said swing secondary windingfor operating the lamp, a separate reactive power factor correcting leadsecondary winding mounted on said core between said lag secondarywinding and said primary Winding, said lead and swing secondary windingsthereby being disposed on opposite ends of said primary winding, acapacitor, and a closed lead circuit connecting said capacitor in serieswith said primary, lead and swing windings in a closed loop with saidwindings additively related.

15. In a discharge lamp ballast, the combination comprising a magneticcore, a primary winding on said core, a separate reactive swingsecondary winding on said core and adjacent one end of said primarywinding, a separate lag secondary winding on said core and spacedthereon from the opposite end of said primary winding, a separate leadsecondary winding disposed on said core adjacent said primary winding, acapacitor, a lead circuit connecting said capacitor in series with saidprimary, swing secondaly and lead secondary windings, and a lag circuitconnecting said primary and lag windings in series with at least part ofsaid swing secondary winding, said primary winding being connected inthe same direction in both said lead and lag circuits.

References Cited in the file of this patent UNITED STATES PATENTS2,496,981 Boucher et al. Feb. 7, 1950 2,683,243 Feinberg July 6, 19542,712,618 Feinberg July 5, 1955 2,774,010 Feinberg Dec. 11, 1956 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION tent N00 2,885,597 May"5, 1959 It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 5, line 35, for "drags" rea for "primary" read terminal Soroccurrence, read terminal 5 69, for

terminal line 69, for swing m 3 column '7 line 42, for "190" read 15C)line 63, for "220" read 218 7Z3, strike out "228; column 8, line 61, for"I235" 236 column 10, line 2, for "148" m 1U column 13, line 23, for"B76" read me 36/ line 235, for 3/0" m 364 =5 41, "coil" read ballast 5both line $7, for "Smooth" smooth Signed and sealed this 6th of. October157990 Attest:

KARL AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of PatentsUNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N0o2,885,597 5, 1959 Liert Ko Naster It is hereby certified that errorappears in the printed specification of the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 5, line 35, for "dz ags draws column 6, line 64., for "primary"read terminal line 66, for "primary", second occurrence, read terminallines '68 69, for "primary" read terminal line 69, for "swing" read leadcolumn 7, line 42', for "190" read 150 line 63, for "220" read 2123 line722, strike out "228"; column 8, line 61, for "235" 236 column 10, line2, for "148" read 12 column 13, line 23, for "370" read M 364 line 25,for "3? read =5 line 41, for "coil" read ballast both occurrences; line5'7, f "samooth" read smooth Signed and sealed this 6th day of. October1959.,

(SEAL) Attest:

KARL E. AXLINE ROBERT c. WATSON Attesting Oflicer Commissioner ofPatents

